AUGUSTA, Ga. - Before he took a single one of his record-low-tying 270 strokes, Jordan Spieth threw a gauntlet right in front of himself. He said early in the week that he wanted to be in the hunt Sunday, "to see what I'm made of."

Now, it is plain to see for Spieth and the rest of the world that he is made of the right stuff.

He met his own challenge, and everything else that the course, the pressure and the field threw at him and won the Masters. He did it at 21, the same age as Tiger Woods in 1997 when he won with the 18-under-par record score that Spieth matched. He shot 2-under 70 Sunday to complete one of the most dominant victories ever seen at Augusta National Golf Club.

Fittingly for someone of his years, he started his onslaught early, taking the lead Thursday and becoming the Masters' first wire-to-wire champion since Raymond Floyd in 1976. In the process, the man from Dallas established himself as a new force in golf, and possibly in American sports.

"This was arguably the greatest day of my life," he said, wearing the green jacket he earned by holding off one last charge from major champions Justin Rose and Phil Mickelson.

The look on his face and the wonder in his voice suggested that Spieth really could drop the "arguably" part. "To join Masters history and put my name on that trophy and to have this jacket forever," he said, "it's something that I can't fathom right now."

Fellow golfers had trouble fathoming how Spieth (rhymes with "teeth") has quickly discovered the knack for taming one of the world's most revered courses. He led after three rounds in his debut here last year, but lost to Bubba Watson, who presented the green jacket to Spieth Sunday night.

What has struck people who have watched Spieth all week is that he has inner qualities that compensate for the fact that he is not the longest driver nor spectacular in any one aspect of the game. "He's going to sort of fly the flag, I think, for golf for quite a while," said Rose, who played with Spieth and several times came within three strokes. The 2013 U.S. Open champion never got closer and lost by four.

Mickelson, who tied Rose for second at 14 under, said of the winner: "He has no weaknesses. And he has that ability to focus and see things clear when the pressure is on, and perform at his best when the pressure is on."

Spieth's father, Shawn, said: "You see it in his eyes. You know what he's got in his heart." The elder Spieth revealed that this Masters has been brewing inside Jordan ever since the family left the course after the final round last year. "You wouldn't want to fall short like that two years in a row. You've got to believe, and he did," Shawn said.

More inspiration came through a Saturday night text from fellow Texan Ben Crenshaw, a two-time Masters champion who made an emotional farewell to the tournament Friday. According to Spieth, Crenshaw's message was: "Stay patient, this is going to be yours . . . Just keep your head down and stay focused."

On the greens, Spieth often looked like Crenshaw, known for his putting skill. In terms of pure style, though, Spieth more resembled the man who hit the first ceremonial tee shot Thursday: Arnold Palmer. Spieth's approach was full speed ahead.

The signature moment came on the par-5 13th hole, when Spieth led Mickelson by four shots and Rose by five. Instead of playing conservatively and laying up in front of the water, he boldly hit for the green, shouting at the ball "Go hard!" The shot landed on the green and stopped 10 feet from the hole. He two-putted for a birdie that brought him back to 18 under.

"I took my mind off this moment for the last week to where I couldn't really express words that would make sense right now. But it is very, very special to join this club," said the young man with the right stuff and a green jacket.